1. Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to electrical switching apparatus such as for example, circuit breakers. The disclosed concept also relates to dampening assemblies for circuit breakers.
2. Background Information
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltage and other fault conditions. Typically, circuit breakers include an operating mechanism, which opens electrical contact assemblies to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions as detected, for example, by a trip unit. The electrical contact assemblies include stationary electrical contacts and corresponding movable electrical contacts that are separable from the stationary electrical contacts.
Among other components, the operating mechanisms of some low and medium voltage circuit breakers, for example, typically include a closing assembly and an opening assembly that are structured to close (e.g., contacts electrically connected) and open (e.g., contacts separated), respectively, the separable contacts. Specifically, the operating mechanism includes a pole shaft, a number of stored energy devices such as, for example, an opening spring and a closing spring, and a latch assembly that cooperates directly or indirectly with the pole shaft to facilitate desired movement of the separable contacts.
The basic components of the latch assembly typically include a D-shaft and a latch (e.g., plate member) that cooperates with the D-shaft, but is disposed on a separate shaft. That is, the latch rotates with the separate shaft about the longitudinal axis of the separate shaft. The D-shaft includes a slot such that it blocks movement of the latch when the D-shaft is disposed in a corresponding range of axial positions, but permits movement of the latch, through the slot, when the D-shaft is disposed in a particular predetermined axial position. Sometimes, however, the D-latch does not come to an ideal resting position during operation, which can have an adverse impact on circuit breaker function. By way of example, if the D-latch is sufficiently out of position, the latch (e.g., trip latch) will not close. Such problems are primarily caused by shock and/or vibration in the system, which can cause components, including the D-shaft, to bounce and/or flutter and ultimately come to rest in an undesirable position.
There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in dampening assemblies therefor.